1. Field of the Invention
The invention relates to a process for removing films of flow agent which cling to moving strip material, in particular of metal. The invention further relates to an apparatus for carrying out that process.
2. Description of the Related Art
Before or during the treatment of moving strip material, for example by rolling, longitudinal cutting, milling etc., it is known that oils, aqueous emulsions or similar flow agents for lubricating or cooling the strip material are applied to the surface of the strip in the processing zone. Even if the major part of the flow agent applied runs off the strip at the side thereof after the processing operation has been carried out, nonetheless there is always still an undesirably large amount of flow agent that remains clinging in the form of a film to the surface of the strip, which causes a great deal of problems and gives rise to difficulties when the processed strip is wound up to form a coil, or is used in subsequent treatment operations (for example annealing or pickling).
Therefore, attempts have already been made to remove the undesired film of flow agent from the surface of the strip by scraper blades of flexible material such as plastics material. When the processed strip is passed between two such blades which come together at their edges, the edges of the blades act as sealing lips and hold back the cushions of flow agent which collect in front of the blades on the top and underside of the strip, the cushions of flow agent then finally dripping off.
However the use of such scraper blades is in no way devoid of problems for, when dealing with surfaces of soft sensitive material, it gives rise to the formation of grooves, scratches and similar surface damage. In addition, the scraper blades are only effective at a relatively low speed of movement of the strip. When the speed of the strip is increased beyond a certain level, the amount of flow agent that ultimately collects in front of the sealing lips is greater than the amount which can drip away in the same amount of time, which means that such devices do not effectively remove the flow agent.
It is also known for moving strips having flow agent films to be passed between pairs of squeeze rollers. Although when that is done the danger of damaging sensitive strip material does not occur, nonetheless at high speeds of movement of the strip, the removal effect is lost for the same reasons as when using sealing lips.
Two pairs of scraper blades have also already been arranged at a defined spacing from each other in the direction of movement of the strip, and extending transversely with respect to the top and underside of the strip, with a vacuum being applied to the space between the two pairs of scraper blades. Although that arrangement provides effective removal of the flow agent even at higher speeds of movement of the strip, nonetheless the disadvantage of scratching sensitive surfaces of strip material still remains. It has therefore hitherto not yet been possible satisfactorily to solve the problem of removing a film of flow agent from treated moving strip material under a wide range of operating conditions.